Well i myself refuse to go on new missions ATM so im still round mission 30 XD

As for MGO tehre are 3 gamemodes.

Team Deathmatch where each kill takes a counter off the enemy team, but if you foulton someone, your team gains the frags that the player you extractd collected in his current life.
A domination mode where its basically controll the points and make the counter tick.
And a sabotage mode. One team is outfited with cloaking equipment and non lethal guns, and the other doesnt have cloak, but has access to their weapons.

The attacking team has to reach 2 points and recover a data tape, then return it to the extraction zone. The defenting team needs to either kill the attacking team, or delay them long enough for the timer to run out.

All matches are 2 round games. If each team has a win each, then points decide the victor. There are gun emplacements and mortars, and also walker gears. Thats about it to the current MGO. Its all done with MGS V gameplay. Also extracting someone is always more beneficial than simply killing them, but the baloon can be shot by team mates so that he is saved. Also you can interogate someone, this reveals all enemy locations on the minimap for a few seconds for your entire team.

You also have 3 classes to choose from. Fast, low health and stealth armed CQC class, heavy slow and tough to bring down support class, and the midle of the road sniper/mid range class.

Each class is its own character and is leveled separately. And you unlock new guns and equipment. Also you are free to pick up enemy equipment after you kill them, but there is a time limit to that.